Sheet-fed rotary offset printing machines customarily are so arranged that sheets are separated from a stack and transported over an alignment or orientation table to a point adjacent the printing machine itself at which the respective sheets are placed, oriented and aligned with respect to lateral and end marks or stops, so that the sheets will be fed accurately both with respect to their longitudinal alignment as well as their end position into the printing system. The sheets, fed separately over the set-up or alignment table, are then transported into the printing machine itself by means of a sheet transport arrangement which is part of the printing system. The sheets are fed to the transport arrangement of the printing machine from the stack by means of a sheet transport conveyor until the sheets engage the front stops or alignment markers of the alignment tables. The sheets which are aligned and engage the forward stops or markers of the alignment table can be moved laterally, perpendicularly to the direction of main movement towards the printing machine, in order to engage lateral edge stops of the alignment table. The drive for the sheet transport arrangement for the alignment transmission ratio.
Sheets transport arrangements of the type described are known from the literature--see, for example, German Patent No. 1,230,041. This patent discloses transport of single sheets which have already passed through a printing machine to a laminating or pasting machine, that is, to transport already printed sheets for subsequent processing. If the speed of the supply arrangement, that is, of the transport conveyor associated with the alignment table is changed, it is necessary to change the operating speed of the alignment table release or stop arrangement as well and, additionally, to change the speed of the sheet feeding system which places the sheets, usually in staggered, overlayed, overlapping arrangement on the alignment table for subsequent transport. This is a disadvantage since the arrangement can no longer be operated in synchronism with a printing machine since proper transfer of a sheet to a printing machine can no longer be assured.
The systems as disclosed use a lateral pull arrangement, operating in synchronized steps, to pull the sheets to a lateral or side marker or stop. These movements usually are only over a short distance; they do require a certain minimum time, however, which may be independent of the operating speed of the machine which processes the sheets themselves. The lateral shifting time can occur only at a well defined time duration and must be terminated when the next sheet reaches the alignment table. This requires a certain minimum overlap distance if the sheets are overlapped when being supplied; the stiffness of the material itself determines the maximal permissible engagement speed of the sheets on the alignment markers or stops of the alignment table. The static loading on the stops and on the sheets also limits the maximum transport speed on the supply table which, then, determines the maximum repetition frequency or cycling frequency of the machine which processes the sheets themselves.
German Patent No. 840,847 discloses a sheet supply arrangement of the type generally referred to. This arrangement differs from that of the foregoing literature reference in that the sheets are transported singly, that is, without overlap, and the system is so designed that any sheet overlap is avoided. Such arrangements result in low operating speed since the cycling time of any sheet processing system--for example a printing system--taking over the separated sheets must be limited to a value which, at the time of the patent, was high, but does not meet current requirements. In other respects as well, the arrangement has the disadvantages of the aforementioned structure.